ABSTRACT Our overarching goal is to better understand the role of post-translational modifications (PTMs) of cellular proteins in cancer with the underlying assumption that the enzymes that catalyze the addition or the removal of these PTMs are candidate therapeutic targets in cancer. While enzymes such as protein kinases have been extensively studied in cancer, new classes of enzymes have recently emerged as potential cancer targets. In particular, more than 100 lysine methyltransferases (KMTs) are predicted to be present in the human proteome and many are implicated in cancer etiology. However, the catalytic activity and substrate specificity for many of these enzymes remains unknown. In particular, functions for the vast majority of the large family of seven ?- strand KMTs are not known. A central hypothesis to be tested here is that uncovering the activities of these orphan KMTs may provide new links between protein lysine methylation signaling and cancer biology. Here we focus on the candidate KMT METTL13 (Methyltransferase-like protein 13) as a potential critical regulator of tumorigenesis. The METTL13 gene is amplified in many cancers and METTL13 mRNA is over- expressed in diverse tumor types, including several were METTL13 expression negatively correlates with patient survival. However, METTL13 is an orphan enzyme and knowledge of any potential substrates and the overall mode of action of this protein in cells and in vivo is obscure. Based on preliminary observations, we hypothesize that METTL13 up-regulates protein translation to promote tumorigenesis. In Aim 1 we characterize the physiologic catalytic activity of METTL13 and the molecular functions of METTL13 in the regulation of eEF1A activity in vitro and in protein synthesis in cells. We will also investigate METTL13 and methylated eEF1A interacting partners and how these pathways intersect to influence cancer cell phenotypes. The goal of Aim 2 is to elucidate the role of METTL13 in tumors driven by oncogenic KRAS. We will test the hypothesis that METTL13, via its methylation activity, cooperates with KRAS signaling to promote the unlimited expansion of cancer cells in vivo using mouse models of pancreatic ductal adenocarcinoma and lung adenocarcinoma, in which the RAS pathway is frequently activated. We will also investigate the tumorigenic role of METTL13 in human tissue using patient-derived xenograft (PDX) models. We will assess the effects of METTL13 loss on protein translation in vivo. Finally, we will explore potential synergies of METTL13 ablation in combination with inhibitors of cell survival and growth pathways in pre- clinical models of pancreatic and lung cancers.